Remotely-controlled video camera systems currently are in use, in which a video camera positioned within a particular area captures and transmits images of the area to a remote viewer terminal over a data path. The received images (i.e., video) may then be displayed to a human operator (or viewer) at the remote viewer terminal.
Some systems include pan-tilt-zoom (PTZ) types of cameras, which are controllable to produce images associated with different fields of vision, where the “field of vision” (or FOV) associated with an image is the extent of the observable world that is conveyed in the image. In such systems, the operator of the remote viewer terminal may remotely control the FOV associated with the images provided by the camera by actuating various PTZ control components (e.g., joysticks) associated with the remote viewer terminal. For example, a remote video camera may be producing images associated with a fixed FOV, and the operator may manipulate a joystick to cause the camera to pan to a different FOV and/or to change the FOV by zooming in or out. Alternatively, if the camera already is panning, the operator may manipulate the joystick to indicate that the operator wants the camera to stop panning, and to provide images associated with a desired FOV. Either way, based on the joystick inputs, the remote viewer terminal sends PTZ directives to the camera (e.g., via the data path) to cause the camera to change its pan angle, tilt angle, or magnification level (e.g., zoom setting) in order to capture images associated with operator-desired FOV.
PTZ control of a video camera by a remote viewer terminal is complicated by the delay associated with the communication loop between the remote viewer terminal and the video camera being controlled. The delay between a remote operator actuating a PTZ control component and the remote operator observing the camera's reaction to the associated PTZ directive typically includes several facets. For example, fixed delays typically include a relatively negligible period of time between the operator actuating a PTZ control component and the remote viewer terminal transmitting an associated PTZ directive, a regular negligible period of time between the camera receiving the PTZ directive and the camera responding accordingly (e.g., by moving the FOV or ceasing such movement), and a relatively significant period of time associated with the processing path between the camera's optics and transmission of the images to the remote viewer terminal (e.g., including various digitization and compression steps). In addition, a relatively significant fixed or variable delay is associated with time that it takes for the remote viewer terminal to process and display a received image (e.g., including various decompression and other image processing steps). Finally, relatively significant, variable, network-imposed delays may be associated with conveying PTZ directives from a remote viewer terminal to the camera, and in conveying encoded images from the camera to the remote viewer terminal. These latter delays may vary based upon the signal conditions of the remote viewer terminal and the camera, the number of attempts necessary to convey a PTZ directive or image, and the current network loading, among other things.
Together, the various delays inherent in a remotely-controlled video camera system may create a frustrating user experience, and in some cases, may render the system un-usable for a particular purpose. For example, one particularly frustrating problem is that of PTZ “overshoot.” In this scenario, an operator at a remote viewer terminal may manipulate a PTZ control component to command the camera to pan in a particular direction until the operator is viewing images associated with a desired field of vision. Once the images associated with the desired FOV are being displayed, the operator may indicate a desire for the camera to stop panning in the previously commanded direction (e.g., by relinquishing command of the PTZ control component). Because of the inherent delays in the communication loop between the remote viewer terminal and the camera, however, the camera overshoots the desired FOV. Once the operator begins viewing images associated with the overshot FOVs, the operator must manually correct the FOV by manipulating the PTZ control component to instruct the camera to move back in an opposite direction from the previously commanded direction. The camera may then overshoot the desired FOV again, leading to a frustrating oscillation. This problem may be even more frustrating when the operator wants to observe a moving object (e.g., a moving car or person). Accordingly, there is a need for methods and apparatus for better compensating for overshoot of a desired FOV in a remotely-controlled video camera system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.